During spinal fusion procedures, a solid bridge is typically formed between the two vertebral segments to limit movement in the section of the spine of the spinal fusion. A common technique for spinal fusion procedures involves the use of interbody cages to fill the gap between the two segments in the spine that are being fused. The addition of bone graft material during the spinal fusion procedure can additionally provide a suitable foundation and environment that allows new bone growth and fuses the area of the procedure over time. Interbody cages can have central cavities that can be packed with bone graft materials. However, packing these central cavities tightly with such material can be difficult because the bone graft materials can fall out of the interbody cage while setting the interbody cage into place since, for example, force can be required to insert the interbody cage into the body.
Others have attempted to solve these problems by constructing interbody cages that are configured to retain bone graft material during spinal fusion procedures. For instance, in U.S. Pat. No. 5,609,635, the disclosed lordotic implant provides a solid cage with a sliding door on the rear face of the device. Even though the configuration disclosed by U.S. Pat. No. 5,609,635 improves upon standard interbody cages, the disclosed lordotic implant has several disadvantages. One example of a disadvantage is that the top and bottom faces of the device are rigid, and thus the disclosed lordotic implant does not allow for maximum graft packing due to the rigidity of the cage. Another disadvantage is that the sliding door of the lordotic implant is located on the rear face of the cage making it difficult to firmly pack the cavity since, for example, additional bone grafting material cannot be easily added to the cage after insertion into the body.
Another attempt to address the above-mentioned problems is described in U.S. Pat. No. 8,715,355, wherein a three-sided cage, with removable plates for top and bottom faces is disclosed. Once inserted between two vertebral bodies, the central cavity is packed with bone graft materials. The top and bottom plates can be removed, and the rear face is covered to contain the graft materials. However, the cavity in the disclosed configuration is difficult to pack tightly. Moreover, the surgeon inserting the disclosed cage in the body faces difficulty in determining the total amount of grafting material that should be inserted into the patient before the rear opening is closed.
Even further, packing the cage after insertion can cause problems since the cage may migrate from the desired location. If such migration occurs, a greater risk to the nerves and/or surrounding anatomy exists when packing the cage after insertion since these structures may be inadvertently damaged during the packing process. Accordingly, the known techniques and, devices for spinal fusion procedures have a number of problems.